Add WalkCrossDevice option to walk policy

Add the walk policy flag WalkCrossDevice to the fswalker Walk calls. This will avoid potential issues when running in a docker container where a FS tree is made of many overlays. Without the flag set, the Walk operation skips over files on devices that do not match the device at the base path.
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Gitea Version: 1.28.0+dev-477-g8b6ad49a5f